Clay Protects From Toxic Sap

a bright blue and yellow macaw hangs upside down with a blurry background

Biological Strategy

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Protect From Chemicals

Chemicals are everywhere in the bodies of living organisms and their external environments. While most chemicals are valuable or benign, some are toxic, including those used for defense (such as the mucus that protects clownfish from an anemone’s stinging tentacles). Even naturally-occurring chemicals, such as arsenic, must be managed to reduce their impact. Some living systems have strategies to break down harmful chemicals, alter them into less toxic forms, physically prevent chemicals from harming sensitive tissues, and more. For example, some herbivorous mammals can digest toxic compounds in plants because they have a particular enzyme that helps them process poisonous plant compounds.

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Birds

Class Aves (“bird”): Eagles, hawks, sparrows, parrots

Birds are evolutionary engineering marvels. They are descended from dinosaurs, but are far from our idea of heavy, scaly reptiles. Of the specific adaptions that set them apart, most notable is flight—although some mammals can fly, birds take the prize for abundance in the skies. Many birds have hollow, lightweight skeletons and specially-designed wings to help them stay aloft. They also have feathers made of keratin that help them stay warm, attract mates, and improve navigation and aerodynamics in flight. In contrast to their dinosaur ancestors, they lack true teeth and have replaced them with specialized beaks and bills.

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Macaws survive ingesting toxic hura seeds because they eat clay.

Image: Wikimedia commons /

Head of the Blue-and-yellow Macaw in the Weltvogelpark Walsrode near Walsrode, Lower Saxony, Germany

Image: Wikimedia commons /

Head of the Blue-and-yellow Macaw in the Weltvogelpark Walsrode near Walsrode, Lower Saxony, Germany

“The hura tree protects its explosive fruits with a sap so toxic that it will raise great red welts if it touches human skin and even blind those who get it into their eyes. The macaws, however, are not put off. Long before the fruits are ripe, the birds rip them apart, pods, seeds and all, and then, after a meal that would have poisoned others, they fly to particular places on a river bank where they can gnaw out and swallow a special clay which detoxifies their meal.” (Attenborough 1995:32-35)

Last Updated August 18, 2016

References

Book

The Private Life of Plants

21/08/1995 | David Attenborough

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